If they really believe that a man is capable of producing a book like this, then challenge them to produce a similar book, if they are sincere about what they are saying
Faridul Haque
So let them bring a single discourse like it, if they are truthful
Hasan Al-Fatih Qaribullah
Let them produce a phrase like it, if what they say is true
If they are true to their word, let them bring a word like it!
Al-muntakhab fi tafsir al-Qur'an al-Karim
Let them, then, produce an informative, discourse, inducing to duties and admonitory, in the similitude of the Quran, if they can truly bring forth their strong reasons